Friday, 11 September 2020

Astrognome 100 Great Stars No 26 Cor Caroli

 

Cor Caroli

Alpha Canes Venatici is the brightest star of the hunting dogs that was created by Johannes Hevelius in the 1670s. It is formed of stars that can be found beneath the handle of the Plough or Big Dipper as it is known as in America.


The name Cor Caroli is modern, the star in ancient Greece was known as ‘Chara’ one of the two hunting dogs. Beta Canes Venatici was known as ‘Asterion’ the second of the hunting dogs. Today we use Cor Caroli and there is some confusion what this refers to.

Cor Caroli means ‘Charles’ Heart’ and one legend says that it represents King Charles II when he was crowned king in 1660, it is said to have shone brightly that night. The other is that is represents King Charles I on the night he was executed when the constellation was seen pointing downwards in respect of the execution of the king.

It is a double star lying at a distance of 115 light years. The two components of the star are formed of an A0 and F2 class stars, the A class star is the brighter. Alpha 2 which is the star we see and call Cor Caroli is slightly variable varying between magnitudes 2.8 and 3.0 which can be detected by an experienced variable star observer.

Cor Caroli is a strange magnetic variable star and is made up of elements similar to those of Chi Lupi, It is in fact the prototype star for a whole group of these magnetically variable stars which spread between A and B class stars with Cor Caroli being in the middle.

Although it is beyond the scope of these notes astronomers study these Cor Caroli type variable stars to try to better understand if there is a link between them and white dwarf stars.

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